Re: waitid() fails with EINVAL for SA_RESTART signals

[Parag Warudkar <kernel-stuff@comcast.net>]

On Thursday 26 May 2005 20:37, Parag Warudkar wrote:

With WCONTINUED - there is no waitid in the strace output -

> clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
> child_tidptr=0x2aaaaade7b70) = 7683
> child (PID = 7683) started
> rt_sigaction(SIGUSR1, {0x400aa0, [], SA_RESTORER|SA_RESTART,
> 0x2aaaaabefca0}, NULL, 8) = 0
> clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
> child_tidptr=0x2aaaaade7b70) = 7684
> write(1, "Error Code from waitid - -1\n", 28Error Code from waitid - -1
> ) = 28

Without WCONTINUED -

>clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, 
child_tidptr=0x2aaaaade7b70) = 7898
>child (PID = 7898) started
>rt_sigaction(SIGUSR1, {0x400aa0, [], SA_RESTORER|SA_RESTART, 0x2aaaaabefca0}, 
>NULL, 8) = 0
>clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, 
child_tidptr=0x2aaaaade7b70) = 7899
>wait4(7898, Sending signal to parent
>0x7fffffffeecc, WSTOPPED, NULL) = ? ERESTARTSYS (To be restarted)
>--- SIGUSR1 (User defined signal 1) @ 0 (0) ---
>--- SIGCHLD (Child exited) @ 0 (0) ---
>write(1, "Caught signal", 13Caught signal)           = 13
>write(1, "\n", 1
>)                       = 1
>rt_sigreturn(0x1)                       = 61

It's of course beyond me why this difference - strace output should have had 
mention of wait4(...) = ENOTSUP (or whatever) when WCONTINUED is used. 
WCONTINUED is declared in include files and mentioned as supported in the man 
pages.

Parag